Hollow gaskets having multiple-channels make excellent sealing strips for refrigerator doors and the like because the multiple channels form insulating dead air spaces throughout the entire inner portion of the gasket and give a certain resilience to the gasket. This compressible yet resilient construction permits a large surface width of the gasket to conform against the frame surface to provide an excellent thermal seal for the door. Such gaskets are well known in the art, for example, U. S. Pat. Nos. 3,178,778 and 2,908,949.
Several improvements to the basic design have surfaced in the development of gasket art. One improvement, for example, involves the creation of one or more central cells, also know as bulbs or balloons, such as those described in U. S. Pat. Nos. 3,952,455 and 4,138,049. The central cells increase the insulating dead air space to enhance the overall insulating quality of the gasket as well as cooperate with the outer walls of the gasket to provide increased flexibility.
Magnetic strips having a flat surface can be used in conjunction with the above-mentioned compressible gaskets to enhance the sealing function. The magnetic strips are usually positioned inside one of the channels of the gasket which is affixed to the door of the refrigerator. The gasket wall is sufficiently thin to allow the strips to magnetically adhere to the refrigerator frame through the gasket walls, thus acting as a magnetic latch.
Since the gaskets usually cannot be employed as one continuous length of material, several sections must be spliced together to form the entire gasket according to the shape of the opening to be sealed (usually rectangular for refrigerator applications). Standard splicing techniques such as heat welding have two major problems associated therewith.
First, the gaskets are usually made of an extruded material such as a PVC compound or the like, and are made with inner and outer walls which are quite thin for enhanced flexibility. As wall thickness decreases, the heat splicing process tends to fuse the thin inner walls to the side walls and to each other, forming what is known in the industry as "hard corners." Hard corners destroy the continuity of the channels of the gasket at the spliced joint and ultimately degrade the insulating quality of the gasket. Further, hard corners are less flexible than the adjoining gasket sections, inhibiting compression around the corner area which also degrades the insulating efficiency of the gasket.
Second, as the area of the central cell increases to provide more flexibility, the overall stiffness of the gasket section decreases, making it difficult to manipulate within the splice mold area. Extremely flexible gaskets have a tendency to escape the tooling of the splice mold, causing frequent and expensive delays for a human operator to correct before the splicing process can be successfully completed.